The research progress on organic nonlinear optical crystal DAST and its application in Teraherz region

Abstract

This article mainly introduces the basic structure and physical performance parameters , several kinds of growth methods about 4- N , N -dimethylamino-4- N -methyl stilbazolium tosylate (DAST) crystal, and generating THz wave based on DAST crystal by optical difference frequency method. The dual wavelength tuning range and beam quality of optical pump sources have an important impact on the conversion efficiency and tuning range of THz in the generation of THz radiation based on DAST crystal by the optical difference frequency (DFG). In addition, the influences of optical pump (the wavelength of femtosecond laser, pulse width and energy) to the THz pulse output enengy and conversion efficiency in the process of generating THz using optical rectification (OR) were also reported. The influence factors of THz radiation and main challenges in the process of growing high quality and large size DAST crystal have been analyzed comprehensively. Bulk single crystal were grown with dimensions of 25 mm×22 mm×2 mm using the slope nucleation coupled with seed crystal method in our present work on systematic analyzing the advantages and disadvantages of spontaneous nucleation method, slope nucleation method, seed crystal method and two zone growth method. Next, we expect to improve laser-THz conversion efficiency and the THz radiation energy by optimizing the process of crystal growth and improving the quality of optical pump.